24+ mpg after 6 weeks on the road

[ShadowsPapa]

Not sure where you guys live but stepping up to 93 in my area is like an extra 50 cents. That's too much an extra mile for me. I would run a tank of 93 through my Cadenza once a year or so because it has some extra detergents in it but that was about it. I figured I wasn't burning it all so it was just a waste ultimately. I was under the assumption that my engine wasn't running hot enough to burn it all. I also put Techron in my tank every other oil change to help with carbon build up as recommended in my manual (very sooty engine).

The extra octane won't save you anything engine-wise. These are tuned for 87.
Octane is ONLY the resistance to self-ignition. There is NO other difference UNLESS you switch to a higher octane that also has other features. But if you took two gasolines from the same company and 1 was 87 and the other was 91 or 93 and they didn't add any other features or detergents to the 91 or 93, the only difference at all is resistance to self-ignition. That's all.
If it's sold as a premium product with cleaners/detergents or other additives, that's different and it's not the octane that's doing that, it's their other additive products.
Higher octane has longer, more complex molecular chains that resist self-ignition.
It doesn't burn slower, it doesn't burn faster, it doesn't have more energy, it doesn't have less energy.
It ONLY resists self-ignition, the cause of detonation in the end.

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[ShadowsPapa]

brother theres so much wrong in that thread i dont have the time to correct it. Youre flat wrong on almost everything you posted.

Really? A college and factory trained tech with 45 years experience - and what's your background.
Go for it - list your expertise and experience - and explain with evidence, what's wrong. Don't just contradict, give references (and I don't mean internet posts from novices - everyone on the internet is an expert - just ask 'em!)

 

[KurtP]

Not sure where you guys live but stepping up to 93 in my area is like an extra 50 cents. That's too much an extra mile for me. I would run a tank of 93 through my Cadenza once a year or so because it has some extra detergents in it but that was about it. I figured I wasn't burning it all so it was just a waste ultimately. I was under the assumption that my engine wasn't running hot enough to burn it all. I also put Techron in my tank every other oil change to help with carbon build up as recommended in my manual (very sooty engine).

i had an original plan on keeping this Vehicle a long time. Better fuel and higher octane prevents knock and reduces carbon build up. I seafoam vehicles a couple times a year. I get premium for under $2 a gallon. Its too easy for me. Again, opinions vary.

 

[KurtP]

Really? A college and factory trained tech with 45 years experience - and what's your background.
Go for it - list your expertise and experience - and explain with evidence, what's wrong. Don't just contradict, give references (and I don't mean internet posts from novices - everyone on the internet is an expert - just ask 'em!)

i dont make arguments of authority. They dont prove anything, no one cares, and a title doesnt mean you did it right.

but since thats what you have to hold onto, i wrote ecm maps for a major engine tuner; and worked for two separate race teams, as well as a race shop.

try going with arguments of merit. “It works like this because of this”. Its ultimately more effective than “im right because i say so and i was a mechanic for 45 years”. Its the intellectual equivalent of using a bullhorn to demand attention. The number of times you continually cite your “experience” in posts leads me to believe youre insecure and have something to prove, and grabbing the bull horn isnt helping figure any of this out.

 

[ShadowsPapa]

i had an original plan on keeping this Vehicle a long time. Better fuel and higher octane prevents knock and reduces carbon build up. I seafoam vehicles a couple times a year. I get premium for under $2 a gallon. Its too easy for me. Again, opinions vary.

Please explain how higher octane reduces carbon. Only if it's also "Better fuel". That means it's the other additives. The molecular chain complexity doesn't change that, it's their "premium fuel additives".
That's not an opinion, that's scientific fact right from the people who make this stuff.
I have no knock of detonation, so it won't do a thing for me but cost more.

 

[ShadowsPapa]

i dont make arguments of authority. They dont prove anything, no one cares, and a title doesnt mean you did it right.

but since thats what you have to hold onto, i wrote ecm maps for a major engine tuner; and worked for two separate race teams, as well as a race shop.

try going with arguments of merit. “It works like this because of this”. Its ultimately more effective than “im right because i say so and i was a mechanic for 45 years”. Its the intellectual equivalent of using a bullhorn to demand attention.

I know how it works, I know about timing, detonation, the cause of detonation, and octane.
What I was talking about, typing, comes right from the fuel people themselves.
I was also basing my typing on what Jeep themselves say the changes were, and what the problems were with the PCM.

 

[KurtP]

Please explain how higher octane reduces carbon. Only if it's also "Better fuel". That means it's the other additives. The molecular chain complexity doesn't change that, it's their "premium fuel additives".
That's not an opinion, that's scientific fact right from the people who make this stuff.
I have no knock of detonation, so it won't do a thing for me but cost more.

you actually dont know. Because you havent logged your ignition timing or knock correction before and after.

at any rate. Im blocking you. My time is too valuable to waste to keep doing this back and forth shit. People will listen to whom they choose to listen.

 

[Sazabi19]

i had an original plan on keeping this Vehicle a long time. Better fuel and higher octane prevents knock and reduces carbon build up. I seafoam vehicles a couple times a year. I get premium for under $2 a gallon. Its too easy for me. Again, opinions vary.

Wish I had prices like that. Here it's $2.15+ for 87. Sure, $2.75/gal isn't a large amount but I'm not sure I personally see the value in it. Glad you're able to for so cheap.

 

[KurtP]

Wish I had prices like that. Here it's $2.15+ for 87. Sure, $2.75/gal isn't a large amount but I'm not sure I personally see the value in it. Glad you're able to for so cheap.

well, as has been mentioned numerous times, it is supposedly tuned to run 87. I had some driving symptoms at part load that made me wonder if better octane wouldnt help, so a few tanks of testing showed i was consistently a mpg higher with the 93. engines are always tuned to adjust for fuel and other factors, so if there is “head room” in the ceiling limit, it will continue to advance to that limit or until knock is detected. So while a 93 octane file is required to make more power; higher octane will prevent detonation and allow the file to be “more consistent” if that makes sense.

now that it isnt as hot i may try it again and see if it still makes the difference that it did. it could have had to pull timing because of heat/humidity that the 93 was preventing that may or may not be a factor now. The right way to do it would be to pull the timing and kc curves but i dont have the tool to do it.

 

[ShadowsPapa]

I found the dyno sheets for my 360 - it shows torque and HP stats from several runs, including timing changes. The peak was 39 degrees total advance. Over that, the numbers dropped.
When timing was back from 39 total (all in, as they used to say) down to 37, the HP went down some fractions, the torque about 1 pound/foot. So a difference of 2 degrees total timing was not enough anyone could feel it. You'd likely never notice even pulling a trailer on a normal day, only on the drag strip.
When timing was backed down to 35 total, then you saw slightly larger numbers dropped - 4 pound/feet, 3 or 4 hp loss. 33 was the biggest drop.
Interesting note - the best numbers came with higher coolant temps as well. I will have to study all the sheets to get the best info from these specific dyno sheets (there are several pages, multiple columns of numbers) but that's the gist of it.
Oh, and it was running 91 octane at that time. I've backed timing off just a tad because I usually run 87 in it, but still don't get detonation. I'd never hear it over the headers and racing mufflers but the plugs show no signs of detonation on them. It might help that I do run ethanol in it - which runs a bit cooler in the chamber.
The reason HP drops as timing increases past a certain point is because you are creating pressure back against the piston as it's just finishing coming up and you don't have the peak where it has the most leverage on the rod/crankshaft. Same for timing too retarded - you miss the best leverage point and are burning the charge after the piston has gotten down far enough there's almost no leverage on the crankshaft.
The only thing I have ever noticed from timing too far advanced in any of my performance engines was - detonation, hard starting/kickback, loss of power.
I cut .024" off the head of my 4.0 and run a 4x4 cam with rather radical ramps and the thing still doesn't ping with the stock timing mapping. I'll have to look at the build write-up I did to see where I figured static or calculated compression would end up, been a while. I run 87 in it and have 33,000 miles on the original plugs and other than seeing some wear, they are clean, zero carbon build-up at all.

For MY JT - there was no loss of power -not that you could tell without a dyno. It's still just as spunky and strong. Some may find my prior posts where I talked about picking my truck up right after the flash - the WOW bit. I mean it was really spunky. The transmission acted like it was put into some sport shift mode like some vehicles have (such as Grand Cherokee and others)
That WILL lose you mpg for sure. Think about it - why is there a choice on some higher end vehicles? Some want the sport feel, shifting like you really mean it or just robbed a bank, others, like my wife don't care for that and want the mpg more than anything.
Since the economy shift mapping is economy for a reason, and they don't program sport mode by default, you know there's a difference in mpg. DUH.
Since mine totally changed in shift pattern, that's got to be some of the mpg drop since the PCM flash.
If it holds gears longer, and drops down gears more easily (mine often drops back more than just one gear now) I expect some MPG.
Spring will tell........ cold weather means stiffer rubber, lower psi, more rolling resistance and so on.

 

[H2OBUG]

Mine got 23 MPG all day ling with the Minivan tires on it. Went to the 35's now I get 15MPG

 

[ShadowsPapa]

Mine got 23 MPG all day ling with the Minivan tires on it. Went to the 35's now I get 15MPG

I'm assuming you used a tool to plug in your new tire size......... and have run the numbers manually over only using the cluster display which may be off if the tire size setting is not correct.
Mine was spot-on as far as odometer compared to GPS and the mpg displayed matches real manual numbers.

Just plugging in tire size isn't enough as the odometer may still be off if only tire maker numbers are used.

OTOH, you are spinning more weight, larger tires, and the engine has lost a certain amount of mechanical advantage over the stock tires.

 

[MrZappo]

Mine got 23 MPG all day ling with the Minivan tires on it. Went to the 35's now I get 15MPG

This ^

My Mojave came with MT tires and she aint so good on gas ... My buddy gets much better mileage but his truck has (basically HT) tires on it and gets way better mileage ...

All this scientific stuff is great ... But these trucks are the very definition of inefficiency. There is not one efficiency based redeeming trait ... Oh wait, the trailer hitch is polished chrome so I got that going for me ...

So, why dont I put on the HT tires ? Cuz mine looks cool ... And with the occasional looks I get from the young 40 year old moms (until I get close enough for them to see me), ill take the mileage hit ...

Its all I got left !!!

 

[Sazabi19]

well, as has been mentioned numerous times, it is supposedly tuned to run 87. I had some driving symptoms at part load that made me wonder if better octane wouldnt help, so a few tanks of testing showed i was consistently a mpg higher with the 93. engines are always tuned to adjust for fuel and other factors, so if there is “head room” in the ceiling limit, it will continue to advance to that limit or until knock is detected. So while a 93 octane file is required to make more power; higher octane will prevent detonation and allow the file to be “more consistent” if that makes sense.

now that it isnt as hot i may try it again and see if it still makes the difference that it did. it could have had to pull timing because of heat/humidity that the 93 was preventing that may or may not be a factor now. The right way to do it would be to pull the timing and kc curves but i dont have the tool to do it.

I always have my music on so rarely hear anything from the engine. Though I believe a few times I have heard something like a metallic ping (metal popcorn popping?). Maybe I'm just paranoid I dunno, but is that the knocking others are hearing? If that's the case maybe I need to step up a grade or so. I haven't noticed any adverse effects myself and also I'm not sure what I'm hearing, if it's anything. And I'm also not sure if I was moving when I heard it before, maybe a rock if I was? I think I heard it when stopped or going very slow before.

I'll also add I've never had any warning lights or messages, other than to service ESS which went away after that 1 drive on a single day.

 

[Sazabi19]

There is not one efficiency based redeeming trait ...

ESS

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